Magnetic and MO recording media are widely employed in various applications, particularly in the computer industry for data/information storage and retrieval purposes. A magnetic medium in, e.g., disk form, such as utilized in computer-related applications, comprises a non-magnetic substrate, for example, of glass, ceramic, glass-ceramic composite, polymer, metal or metal alloy, typically an aluminum (Al)-based alloy such as aluminum-magnesium (Al—Mg), having at least one major surface on which a layer stack comprising a plurality of thin film layers constituting the medium are sequentially deposited. In the case of longitudinal type magnetic recording media, such layers may include, in sequence from the substrate deposition surface, a plating layer, e.g., of amorphous nickel-phosphorus (Ni—P), a polycrystalline underlayer, typically of chromium (Cr) or a Cr-based alloy such as chromium-vanadium (Cr—V), a longitudinally oriented magnetic layer, e.g., of a cobalt (Co)-based alloy, and a protective overcoat layer, typically of a carbon (C)-based material, such as diamond-like carbon (DLC), having good mechanical (i.e., tribological) and corrosion resistance properties.
Perpendicular type magnetic recording media typically comprise, in sequence from the surface of a non-magnetic substrate, an underlayer of a magnetically soft material, at least one non-magnetic interlayer or intermediate layer, a vertically (i.e., perpendicularly) oriented recording layer of a magnetically hard material, and a protective overcoat layer.
A similar situation exists with magneto-optical (MO) media, wherein a layer stack is formed which comprises a reflective layer, typically of a metal or metal alloy, one or more rare-earth thermo-magnetic (RE-TM) alloy layers, one or more dielectric layers, and a protective overcoat layer, for functioning as reflective, transparent, writing, writing assist, and read-out layers, etc.
According to conventional manufacturing technology, a majority (if not all) of the above-described layers constituting multi-layer longitudinal and perpendicular magnetic media, as well as MO recording media, are deposited by means of cathode sputtering processing. For example, the magnetic recording layers are typically fabricated by sputter depositing a Co-based alloy film, wherein the alloying elements are selected to promote desired magnetic and microstructural properties. In the case of longitudinal-type magnetic disk recording media, metallic and metalloidal elements, such as, for example, Cr, Pt, Ta, B, and combinations thereof, have been found to be effective. Similar alloying elements have been found to be useful in the case of perpendicular-type magnetic disk recording media, and in addition, reactive sputter deposition of the Co-based alloys in an oxygen (O2)-containing atmosphere to form so-called “granular” magnetic recording layers/media has been found to be especially effective in controlling (i.e., limiting) exchange coupling between adjacent magnetic grains. In a typical reactive sputtering process utilized for formation of “granular” perpendicular-type magnetic recording media, O2 gas is mixed with an inert sputtering gas, e.g., Ar, and is consumed by the depositing Co-based alloy magnetic film.
FIG. 1 is a simplified, schematic, perspective view of a portion of a conventional reactive sputtering apparatus 1 which may be utilized for performing reactive sputtering of magnetic thin films as part of the process for manufacturing disk-shaped magnetic recording media. As illustrated, the apparatus comprises a vacuum chamber 16 equipped with an opening for connection to a pumping means for evacuating the interior of the chamber; at least one, preferably a pair of facing sputtering targets or sources of conventional type, e.g., a pair of magnetron sputtering guns; a means for positioning a substrate/workpiece in the space between the pair of facing sputtering sources, illustratively a disk-shaped substrate for a magnetic recording medium, for receipt of sputtered particle flux therefrom on both substrate surfaces; and a gas injector having a gas inlet portion extending outside the chamber and connected to a source of a gas, e.g., a mixture of a reactive gas (such as O2) and an inert sputtering gas (such as Ar), and a gas outlet portion within the chamber, for injecting the gas or gas mixture into the space between the pair of facing sputtering sources. Illustratively, the gas injector is “wishbone”-shaped, and comprises a linearly elongated, tubular inlet portion having a first, gas inlet end, and a second end, with a pair of arcuately-shaped, tubular gas outlet portions extending from the second end, comprising a plurality of spaced-apart gas outlet orifices.
The recording layer(s) of the above-mentioned “granular” perpendicular magnetic disk media is (are) typically formed by reactive sputtering at higher pressures than those utilized for the manufacture of “conventional” longitudinal and perpendicular magnetic recording media. Specifically, the recording layer(s) of “granular” perpendicular media is (are) typically formed at about 30 mTorr, whereas the recording layer(s) of “conventional” longitudinal and perpendicular magnetic recording media is (are) typically formed at about 5 mTorr or less. For one-disk-at-a-time sputtering apparatus utilized in the hard disk manufacturing industry, e.g., the Intevac MDP-250 (Intevac Co., Santa Clara, Calif.), the interval for filling and stabilizing the gas pressure in the process chamber at the high operating pressures required for the “granular” perpendicular media can be a significantly limiting factor in obtaining adequate manufacturing throughput for economic competitiveness. This is due, in part, to the relatively long time constants of the active gas flow controllers conventionally employed in the hard disk manufacturing industry, which conventional controllers require sensing of the thermal conductance of the flowing gas, and to the limited operating ranges of such type controllers.
In view of the foregoing, there exists a clear need for improved means and methodology for providing a burst of gas to a low pressure (i.e., vacuum) processing chamber, e.g., a reactive sputtering chamber, for rapidly cycling between preselected lower and higher gas pressures, in order to achieve increased processing throughput. Specifically, there exists a need for improved means and methodology for manufacturing magnetic recording media, e.g., “granular” perpendicular media in the form of hard disks, by reactive sputtering techniques performed at throughput rates consistent with the economic requirements of automated manufacturing processing. In particular, there exists a need for improved means and methodology for overcoming the above-described drawbacks and disadvantages associated with reactive sputtering processing for the manufacture of hard disk magnetic and MO recording media utilizing conventional gas flow controllers, notably their relatively long time constants and limited operating ranges.
The present invention addresses and solves the problems, disadvantages, and drawbacks described supra in connection with conventional one-at-a-time means and methodology for performing reactive sputtering, e.g., of oxide-containing perpendicular recording layers of “granular” magnetic media, while maintaining full compatibility with all aspects of conventional automated manufacturing technology for hard disk magnetic and MO recording media. Further, the means and methodology afforded by the present invention enjoy diverse utility in the manufacture of all manner of devices and products requiring formation of thin films by means of reactive sputtering processing.